The invention relates to a tool for crushing coke comprising:                a housing that, in an operating state, is fastened to a drill rod, and in which is arranged        at least one cutting nozzle for cutting and a drilling nozzle for drilling coke by means of a water jet, and        a control for supplying water flowing through the housing under pressure for drilling or cutting,        wherein the control for switching the tool from a drilling mode to a cutting mode and vice versa comprises a control device that is rotatable about a longitudinal axis of the housing to switch the tool,        wherein the drilling or cutting mode is set depending on the angular position of the control device.        
In oil refineries, the last, otherwise no longer usable, fraction of crude oil is converted to coke. The conversion occurs by introducing this fraction into upright drums that have a large capacity and, for example, possess a height of approximately 40 m and a diameter of, for example, 8 m. The drums fill with coke over time during operation. When the maximum fill level of a drum is reached, the coke is cut out of the drum. This process, called “decoking”, is performed with high-pressure water jets which crush the coke in the drum and flush it out of the drum.
A tool for generating the high-pressure water jets is fastened to a drill rod, to which water is supplied under high pressure, and the tool is introduced with the drill rod into the drum from above.
First, the tool, in so-called drilling mode, drills a continuous, coaxial opening from top to bottom, wherein the high-pressure water jets exit from drilling nozzles normally arranged at the bottom end of the tool in order to crush the coke. Then the tool with the drill rod is lifted and returned to the top end of the drum. At this location, the tool switches from drilling mode to cutting mode in which the path of flow of the pressurized water to the drilling nozzles is blocked, and instead, flow paths are released to the cutting nozzles that are located on the perimeter of the tool and from which the high-pressure water jets exit substantially perpendicular to the longitudinal axis of the tool and the drill rod, and crush the coke across the cross-section of the drum in a spiral path. The tool executes a rotary movement with the drill rod in drilling mode and in cutting mode as well. Coke crushed in this manner is rinsed out of the drum at the bottom.
The tool is switched from drilling mode to cutting mode and vice versa by rotating the control device by an angle required for the switchover that is usually 90°. The switchover is automatically triggered by significant reduction of the operating pressure of the water from approximately 300 to for example 15 bar as, for example is known from the document DE 10 2007 063 329.
The knowledge of whether the tool is in drilling or cutting mode is especially important for using the tool because a continuous coaxial opening is first drilled in the coke mass with the tool from top to bottom before the coke containers are drained as described above. The mode in which the tool is before being introduced, is generally unknown. Without any clear knowledge of whether the tool is actually in drilling mode as required, drainage of a filled coke drum should not be initiated.
The object is therefore to create a possibility for the operating personnel to obtain a clear understanding of whether the tool is in drilling or cutting mode independent of whether the tool is just being introduced, or whether the draining of the drum should be continued.